The present invention generally relates to machinery and systems for tufting carpets. In particular, the present invention relates to an improved puller roll assembly for a tufting machine.
In addition to yarn feed systems and/or pattern yarn feed attachments, tufting machines generally include pairs of toothed puller rolls that tension yarns from the yarn feed mechanism or attachments to needles of the tufting machines. Such puller roll systems typically consist of a drive roll and an idler roll that operate in a rotating, intermeshing relationship. As the rolls rotate, the yarns are engaged and pinched between the teeth of the puller rolls, which engage in an intermeshing fashion, defining a yarn pinch area between the rolls. The yarns are engaged and pinched between the teeth of the puller rolls as they pass through the pinch area, such that the rotation of the rolls causes the yarns to be tensioned between the rolls for feeding to the needles.
With such traditional puller roll systems as described above, there generally is only a limited area or point of contact at which the yarns are pinched and pulled between the puller rolls. As a result of such limited contact of the yarns with the rolls, the yarns therefore must be tightly engaged or pinched between the teeth of the rolls to try to limit slippage and to thus provide consistent tensioning and feeding of the yarns through the system. As a result, the spacing and intermeshing of the rolls is critical for achieving a uniform, substantially constant flow of the yarns through the rolls without significant slippage or misfeeding of the yarns. As a consequence, it generally has been necessary to monitor and make frequent adjustments to the positions and spacings between the rolls to compensate for the feeding of different sizes or thicknesses of yarns. Such adjustments typically are made manually through the use of adjustment shims, which manual adjustments often are not sufficiently precise, and thus can necessitate additional adjustments. Furthermore, the pinching of the yarns by the rolls can damage or cause breaking of the yarns if the spacing or pinching is too tight or can cause jamming of the rolls if knots are passed therebetween, resulting in misfeeding of the yarns.
There is, therefore, a need for an improved puller roll system that can securely and consistently tension yarns of various sizes to the needles of a tufting machine without requiring continuous adjustment of the puller rolls.
Briefly described, the present invention relates to an improved puller roll system for feeding yarns to the needles of a tufting machine. According to one embodiment of the invention, the puller roll system includes at least one driven puller roll and a pair of floating puller rolls. The driven and floating puller rolls each include radially projecting teeth, and the floating puller rolls are mounted in an intermeshing relationship with the driven puller roll so that the floating puller rolls are rotated with the rotation of the driven puller roll. A yarn engagement path is defined between the driven puller roll and the floating puller rolls along which the yams are received and are passed in a winding, substantially serpentine path. The puller rolls engage the yarns along the engagement path at multiple points or areas of contact with the yarns being engaged between both of the floating puller rolls and the driven puller roll and with the yams being wrapped about a portion or wrap area of the driven puller roll.
As a result, the amount and/or area of contact between the yarns and the puller rolls is substantially increased so that the yarns can be securely tensioned through the engagement path towards the needles without requiring the yarns to be pinched tightly between the puller rolls. In addition, due to the increased areas and amount of contact along which the puller rolls engage the yams, the puller roll system of the present invention can be used to tension various types and sizes of yarns without requiring frequent adjustments of the positions of or spacings between the puller rolls. Consequently, the puller roll system of the present invention enables looser spacing between the puller rolls, with the spacings being set at a distance sufficient to enable a minimum engagement and contact between the yarns and the teeth of the puller rolls sufficient to tension the yarns without the yarns necessarily being tightly pinched between the rolls, which reduces the likelihood that the yarns will be damaged by the puller rolls.
Various object features and advantages of the present invention will become apparent to those of skill in the art upon reading the following detailed description in view of the accompanying drawings.
FIG. 1 is a side view schematically illustrating a tufting machine including a puller roll system according to one embodiment of the present invention.
FIG. 2 shows a cut-away, back side view of the puller roll system of the present invention.
FIG. 3 is an end view, with portions removed, of the puller roll system of FIG. 1.
FIG. 4 shows a cross-sectional view of the puller roll system of the present invention taken along section Axe2x80x94A of FIG. 2.